myelin

Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

n. A white fatty material, composed chiefly of lipids and lipoproteins, that encloses certain axons and nerve fibers. Also called medulla.

from Wiktionary, Creative Commons Attribution/Share-Alike License

n. A white, fatty material, composed of lipids and lipoproteins, that surrounds the axons of nerves.

from the GNU version of the Collaborative International Dictionary of English

n. A soft white substance constituting the medullary sheaths of nerve fibers, and composed mainly of cholesterin, lecithin, cerebrin, protein, and some fat.

n. One of a group of phosphorized principles occurring in nerve tissue, both in the brain and nerve fibers.

from The Century Dictionary and Cyclopedia

Resembling myelin: said of lecithin which has been placed in water and has become swollen and pasty. On microscopical examination it will then be seen to exist in the form of peculiar slimy droplets and threads, which are known as the myelin forms of the substance.

n. In anatomy, the white substance of Schwann, or medullary sheath of a nerve.

n. a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers

Etymologies

From Ancient Greek μυελός (myelos, "marrow") + -in (Wiktionary)

Examples

For the first time researchers at the Krembil Neuroscience Centre, Toronto Western Hospital have successfully transplanted adult spinal cord stem cells into mice and rats to produce the protective cover, known as myelin, which is necessary to insulate the nerves in the central nervous system.

They have also been trying to figure out why the patients with multiple sclerosis lose the protective coating, called myelin, surrounding their axons, the part of the nerve cell that conducts electrical impulses.

Some axons are wrapped in a multi-layer coating, known as the myelin sheath, which helps insulate the axon from other axons, surrounding tissues and fluids and prevents the electrical charge from escaping from the axon.

Nerves that must stimulate organs requiring rapid response—for example, those that might signal the need to remove a finger from a hot surface, or power a leg muscle to run from a hungry lion—are electrically insulated by a fatty molecular layer, a nonconducting lipid sheath known as myelin.